A squeeze on the arm could save lives in heart surgery

COULD the humble blood-pressure cuff hold the secret to a life-saving new treatment? Briefly restricting blood flow to a person's arm seems to prime the heart and other organs to cope with a more severe loss of their blood supply.

The technique could improve recovery from surgery, a heart attack or stroke. "There's tremendous interest because it's a simple, cheap and non-invasive form of protection," said Derek Yellon of University College London at a conference on the approach in London last month.

The effect relies on a phenomenon called ischaemic conditioning, first seen in animal experiments that temporarily cut off the heart's blood supply. Researchers found that there was less damage to the heart if its blood supply was briefly lowered beforehand. It was as if the heart muscle had been trained to withstand oxygen deprivation.

Surprisingly, reducing blood supply in one of the animal's limbs, simply by squeezing it, produced the same benefit. The effect could even be passed from one animal to another with a blood transfusion, suggesting that the squeezed limb released some sort of beneficial chemical signal into the blood. Researchers are now trying to uncover the exact mechanism involved.

Using the method in the clinic involves four cycles of inflating a blood-pressure cuff for five minutes, then deflating it for five minutes. Several studies show that this cuts damage to heart muscle by about one-third following surgery to bypass blocked arteries, when the heart's blood supply must be stopped for up to an hour. It can also be used before the artery-widening treatment given immediately after a heart attack, to lessen damage caused by the sudden return of blood.

Such studies suggest that ischaemic conditioning can lower death rates by as much as two-thirds. But not all trial results have shown a significant effect, although none has found the technique to cause harm. We need to wait for evidence from larger trials, says Gerd Heusch of the University of Essen in Germany, who carried out one of the artery-bypass studies.

Even so, a few hospitals in India and China are already using ischaemic conditioning before heart surgery or as a treatment for heart attacks. In Europe, a computer-controlled cuff that carries out the procedure will be launched later this year. It is already on trial in ambulances in several countries for use following heart attacks.

Work on animals suggests the technique also benefits the brain and other organs. It is now being investigated as a treatment for newborns deprived of oxygen and adults after a stroke, as well as before organ transplants.

"All the data so far suggest that if you get the right patient and you deliver it in the right way, you can have profound effects," says Andrew Redington of the Hospital for Sick Children in Toronto, Canada. "But people can't believe it – it seems too simple."

This article appeared in print under the headline "Squeeze the arm, protect the heart"

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